I don't have nearly as long of hair as you do....LOL.
When I show, I normally do two french-braided pigtails. It did take some time to learn how to do it, but it works really well. After I braid them, I cross them at the back, tucking them in and around each other (really low on the back of my head) and bobby pin the crap out of it. I also use a fair amount of hair spray....I do not even need to use a hair net amount of hair spray.
However....with your hair, it might be too long to do that. You might be better off with just a french braid, and then making it into a bun of sorts. Make sure that the bun sits below your helmet, but will not interfere with the position of it.